Wellbores formed in subterranean hydrocarbon reservoirs enable recovery of a portion of the hydrocarbons using production techniques. The hydrocarbons can adhere to the reservoirs, for example, due to a combination of capillary forces, adhesive forces, cohesive forces, and hydraulic forces. Steam-assisted gravity drainage (SAGD) is an example of an enhanced hydrocarbon recovery technique in which heated treatment fluids (for example, steam) can be applied to the formation to facilitate and enhance recovery of the hydrocarbons that are adhered to the formation. In an implementation of the SAGD technique, an injection wellbore can be formed adjacent to a production wellbore, and the heated treatment fluids can be injected through the injection wellbore into the formation surrounding the production wellbore. The heated fluids can decrease an adherence of the hydrocarbons to the formation, thereby releasing the hydrocarbons into the production wellbore.
While forming (for example, drilling) the injection wellbore, knowledge of a location of the production wellbore relative to the injection wellbore can be important. Traditional surveying techniques provide an estimate location for individual well bores. However, due to a large size of the cone of uncertainty associated with such measurement, a more accurate measurement is required in SAGD or similar applications. Ranging is an example of a method to control a position of a wellbore being drilled relative to an existing wellbore. In ranging, an electromagnetic field from the existing wellbore provides electromagnetic signals received by sensors in the wellbore being drilled. Several conditions, for example, wellbore drilling conditions, can adversely affect an ability of the electromagnetic sensors to sense the electromagnetic signals, and, consequently, affect ranging in the wellbores.
Like reference symbols in the various drawings indicate like elements.